Influenza occurs with seasonal variations and reaches peak prevalence in winter, with many people killed worldwide every year. Until now, only a few organic compounds including amantadine, rimantadine and ribavirin have been used for influenza therapy. However, drug-resistant influenza viruses are generated quickly. The mutation of coat protein genome of influenza viruses severely influenced the antigen expression thereof and new influenza virus mutants are generated. Appearance of Influenza A (H1N1) virus is one of the examples in recent years.
Influenza A (H1N1) virus belongs to an influenza virus type A and is grouped as subtype H1N1 according to haemagglutinin and neuraminidase of the surface antigens. At present, most patients infected with influenza A (H1N1) virus are dosed with Tamiflu® (oseltamivir), the preferred therapeutic drug. Oseltamivir is a neuraminidase inhibitor, which inhibits the neuraminidase activity of influenza virus types A and B. It prevents the release of new virus particles made from the infected host cells, so that replication and transmission of influenza virus are stopped. At present, Tamiflu-resistant viruses are also appeared. Therefore, preparation of pharmaceutical composition particularly on treating influenza A (H1N1) virus becomes an important issue.
In addition to the chemical drugs from synthesis, the natural products obtained from medicinal plants also are the opportunity for developing anti-influenza virus drug. According to the anti-virus screen, the extracts of F. assa-foetida (Umbelliferae or Apiaceae) showed significant potency against influenza A virus (H1N1). The roots of this plant originally were an important remedy for “Spanish flu” (type A influenza, H1N1 subtype) in 1918. However, there is no further researches to explore anti-influenza A virus (H1N1) activity of the pure compounds from F. assa-foetida on within nearly one hundred years.
It is therefore attempted by the applicant to deal with the above situation encountered in the prior art.